1. Field of the Invention
The present invention relates to microwave stages generally and more specifically to a combination thereof, combined for more economical power supply utilization.
2. Description of the Prior Art
Heretofore, it has been relatively difficult to make the most economical utilization of many power supplies. Consider, for example, the prior-art-type (microwave) amplifier stage which is illustrated in (the lower portion of) FIG. 1 of the drawing generally designated by the number 10. Stage 10 includes a field-effect transistor (FET), designated 14. Transistor 14 is configured with the transistor source (electrode) coupled to circuit ground (common) both by a source-biasing resistor 16 and by a source-bypassing capacitor 18; the transistor gate (electrode) both coupled to circuit ground by a (microwave, microstrip-line) gate-biasing stub 20 and coupled to a line 24 by a DC-blocking capacitor 26; and the transistor drain (electrode) both coupled to a line 28 by another DC-blocking capacitor 30 and coupled to a node 32 by a drain-biasing stub 34. Node 32 is also coupled to circuit ground by a biasing-stub-bypassing capacitor 36 and coupled to a line 38 by a drain-biasing resistor 40. Line 38 is connected to a positive-power-supply potential which is developed with reference to a negative-power-supply potential which is connected to (common with) circuit ground.
Source-biasing resistor 16 is used to establish the desired, transistor 14, drain-to-source, biasing current. For example, if it were desired to operate transistor 14 with a drain-to-source current of 50 milliamperes, with a gate-to-source potential of -1 volt, a resistor having a resistance of 20 ohms would be used. Drain-biasing resistor 40 is used to drop the excess power-supply potential. For example, if it were desired to operate transistor 14 with a drain-to-source potential drop of 7 volts and if the available power-supply potential were 15 volts, resistor 40 would be used to drop the excess power supply potential of 7 volts. (In this example, one volt is dropped across source-biasing resistor 16.) Thus, with a drain-to-source current of 50 milliamperes, a resistor having a resistance of 140 ohms would be used.
It is no doubt apparent that a considerable portion (47% in this example) of the energy obtained from the power supply is dissipated (wasted) in drain-biasing resistor 40 (7% being dissipated in source-biasing resistor 16). The energy dissipated in resistor 40 (and in resistor 16) represents energy which the power supply must supply and heat which must be removed from the stage. Also, the energy/heat may degradate the reliability of the stage.
Also illustrated in (the upper portion of) FIG. 1 is another type stage 10' which is similar to the stage just discussed (stage 10). (For clarity, similar components are similarly designated; however, numbers designating components in the latter stage (stage 10') each include a prime mark to distinguish the number (component) from the corresponding (similar) number (component in the former stage (stage 10).)
It is important to note that stages 10 and 10' are both DC and AC independent. In other words, the DC operation (the DC biasing currents and DC biasing potentials) of stage 10 are totally independent of that (those) of stage 10', and vice versa, at least to the extent that the power supply impedance may be ignored. Also, the amplification of an AC signal by stage 10 is totally independent of the amplification of an AC signal by stage 10', and vice versa. In other words, stages 10 and 10' may be used each to amplify a respective one of a pair of signals which are similar, which are different in phase or amplitude, or which are totally dissimilar.
For purposes of discussion, stages 10 and 10' are shown connected each to be driven by a respective one of a pair of phase quadrature signals developed by a (microwave, microstripline) 3 db coupler 42 from an input signal 44 and each to drive another 3 db coupler 46 which develops a single output signal on a line 48.